This invention relates to a method and apparatus for the electrolytic generation of arsine having automatic arsine monitoring and controls to a semiconductor furnace or reactor.
The use of gaseous hydrides in the semiconductor industry has been important from the days of germanium to the present manufacture of Group III-IV devices. Of the hydrides, arsine has been prominent because of its usefullness and its toxicity. Arsine is used as a convenient source for arsenic as a dopant for silicon and for the epitaxial growth of GaAsP. Because of this toxicity with a TLV of 0.05 PPM, the concentration is compressed gas cylinders with hydrogen is kept below 15 percent. The handling facilities, safety equipment, and peripheral instruments necessary to adequately monitor, store, and use this gas are complicated and expensive. Since arsine is almost always used at the input of a reactor whose run time is limited, it would be highly desirable to have a source of arsine that could be easily turned off as from an in-situ cell generator where only the required amount of arsine gas would be generated upon demand, thus eliminating the storage of highly pressurized cylinders of poisonous arsine gas.
U.S. Pat. No. 1,375,819, issued Apr. 26, 1921 to Henry Blumenberg, Jr., discloses a method for the preparation of arsine by the electrolysis of a salt or oxide of arsenic in the presence of sulphuric acid and potasium sulphate or other compounds capable of liberating nascent hydrogen upon electrolysis. However, the process as described fails to provide a sufficient concentration of arsine required by present day semiconductor processing in addition to failing to separate the generated oxygen from the generated arsine within the cell thereby giving separate sources for each.
Accordingly, an object of the present invention is to provide a method for the electrochemical generation of arsine in a self-contained electrolytic cell.
Yet another object of the present invention is to provide an electrochemical generator system for supplying arsine to a semiconductor reactor or furnace have automatic arsine monitoring and controls therewith.
Another object of the present invention is to provide a method for the production of arsine that can be easily regulated and turned off as required.
Still another object of the present invention is to provide separate sources for oxygen and arsine from an electrochemical generator.
It is still yet another object of the present invention to provide a method for generating of arsine a gas concentration of about 20-38 percent arsine.